<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #contentDiv{
            width: 500px;
            height: 150px;
            display: flex;
        }
        #midBtn{
            display: flex;
            flex-direction: column;
            justify-content: center;
        }
        #rightSelect{
            width: 100px;
        }
    </style>

    <script src="work2.js"></script>
</head>
<body>
    <div id="contentDiv">
        <select multiple id="leftSelect">
            <option>China</option>
            <option>Japan</option>
            <option>Spanish</option>
            <option>America</option>
            <option>England</option>
        </select>
        <div id="midBtn">
            <input type="button" value=">" onclick="toRight()">
            <input type="button" value=">>" onclick="toRightAll()">
            <input type="button" value="<" onclick="toLeft()">
            <input type="button" value="<<" onclick="toLeftAll()">
        </div>
        <select multiple id="rightSelect"></select>
    </div>
</body>
</html>